The filmic labels have conventionally been labels containing a white mineral filler, such as titanium dioxide (TiO2), in the plastic material. The addition of the white mineral filler has guaranteed good opacity properties and increased print contrast, and thus the label fulfils the criteria of a good printing substrate. The addition of the white mineral filler has, however, caused problems in the label manufacturing process. The white mineral filler is a very hard material and therefore it wears cutting tools during die-cutting operations.
Another option to build a pressure-sensitive filmic label has been disclosed in US 2005/0187104. The publication discloses in its preferred embodiment that a polymer film is co-extruded and stretched in at least one direction. The polymer film comprises a polymeric image-receiving layer and a layer containing polylactic-acid-based material and dispersed inorganic or organic particles or microbeads as void initiators. The void initiators cause the formation of voids in the layer.
The stretching can only be accomplished in the direction of the plane of the film. A drawback related to the above-mentioned polymer film is that the voids tend to flatten irreversibly e.g. when the film is stored in a roll form, or otherwise pressed. This is quite problematic since roll-to-roll operations are typical label manufacturing processes, and also pressing may take place during these processes.